import 'package:flutter/material.dart';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        // This is the theme of your application.
        //
        // TRY THIS: Try running your application with "flutter run". You'll see
        // the application has a purple toolbar. Then, without quitting the app,
        // try changing the seedColor in the colorScheme below to Colors.green
        // and then invoke "hot reload" (save your changes or press the "hot
        // reload" button in a Flutter-supported IDE, or press "r" if you used
        // the command line to start the app).
        //
        // Notice that the counter didn't reset back to zero; the application
        // state is not lost during the reload. To reset the state, use hot
        // restart instead.
        //
        // This works for code too, not just values: Most code changes can be
        // tested with just a hot reload.
        colorScheme: ColorScheme.fromSeed(seedColor: Colors.deepPurple),
      ),
      home: const MyHomePage(title: '线性布局和弹性布局'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key, required this.title});

  // This widget is the home page of your application. It is stateful, meaning
  // that it has a State object (defined below) that contains fields that affect
  // how it looks.

  // This class is the configuration for the state. It holds the values (in this
  // case the title) provided by the parent (in this case the App widget) and
  // used by the build method of the State. Fields in a Widget subclass are
  // always marked "final".

  final String title;

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;

  void _incrementCounter() {
    setState(() {
      // This call to setState tells the Flutter framework that something has
      // changed in this State, which causes it to rerun the build method below
      // so that the display can reflect the updated values. If we changed
      // _counter without calling setState(), then the build method would not be
      // called again, and so nothing would appear to happen.
      _counter++;
    });
  }

  @override
  Widget build(BuildContext context) {
    // This method is rerun every time setState is called, for instance as done
    // by the _incrementCounter method above.
    //
    // The Flutter framework has been optimized to make rerunning build methods
    // fast, so that you can just rebuild anything that needs updating rather
    // than having to individually change instances of widgets.
    return Scaffold(
      appBar: AppBar(
        // TRY THIS: Try changing the color here to a specific color (to
        // Colors.amber, perhaps?) and trigger a hot reload to see the AppBar
        // change color while the other colors stay the same.
        backgroundColor: Theme.of(context).colorScheme.inversePrimary,
        // Here we take the value from the MyHomePage object that was created by
        // the App.build method, and use it to set our appbar title.
        title: Text(widget.title),
      ),
      body: LinearLayoutDemo(),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: const Icon(Icons.add),
      ), // This trailing comma makes auto-formatting nicer for build methods.
    );
  }
}

class LinearLayoutDemo extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return SingleChildScrollView(
      child: Padding(
        padding: const EdgeInsets.all(16.0),
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: <Widget>[
            Text('线性布局示例:'),
            Row(
              mainAxisAlignment: MainAxisAlignment.center,
              children: <Widget>[
                Text(" hello world "),
                Text(" I am Jack "),
              ],
            ),
            SizedBox(height: 16),
            Row(
              mainAxisSize: MainAxisSize.min,
              mainAxisAlignment: MainAxisAlignment.center,
              children: <Widget>[
                Text(" hello world "),
                Text(" I am Jack "),
              ],
            ),
            SizedBox(height: 16),
            Row(
              mainAxisAlignment: MainAxisAlignment.end,
              textDirection: TextDirection.rtl,
              children: <Widget>[
                Text(" hello world "),
                Text(" I am Jack "),
              ],
            ),
            SizedBox(height: 16),
            Row(
              crossAxisAlignment: CrossAxisAlignment.start,
              verticalDirection: VerticalDirection.up,
              children: <Widget>[
                Text(" hello world ", style: TextStyle(fontSize: 30.0)),
                Text(" I am Jack "),
              ],
            ),
            SizedBox(height: 32),
            CenterColumnRoute(),
            SizedBox(height: 32),
            Container(
              color: Colors.green,
              child: Padding(
                padding: const EdgeInsets.all(16.0),
                child: Column(
                  crossAxisAlignment: CrossAxisAlignment.start,
                  mainAxisSize: MainAxisSize.max,
                  children: <Widget>[
                    Container(
                      color: Colors.red,
                      child: Column(
                        crossAxisAlignment: CrossAxisAlignment.start,
                        children: <Widget>[
                          Text("hello world "),
                          Text("I am Jack "),
                        ],
                      ),
                    ),
                    SizedBox(height: 100),
                  ],
                ),
              ),
            ),
            SizedBox(height: 32),
            Text('弹性布局示例:'),
            FlexLayoutTestRoute(),
            SizedBox(height: 32),
          ],
        ),
      ),
    );
  }
}

// 弹性布局演示
class FlexLayoutTestRoute extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Column(
      crossAxisAlignment: CrossAxisAlignment.start,
      children: <Widget>[
        Flex(
          direction: Axis.horizontal,
          children: <Widget>[
            Expanded(
              flex: 1,
              child: Container(
                height: 30.0,
                color: Colors.red,
              ),
            ),
            Expanded(
              flex: 2,
              child: Container(
                height: 30.0,
                color: Colors.green,
              ),
            ),
          ],
        ),
        Padding(
          padding: const EdgeInsets.only(top: 20.0),
          child: SizedBox(
            height: 100.0,
            child: Flex(
              direction: Axis.vertical,
              children: <Widget>[
                Expanded(
                  flex: 2,
                  child: Container(
                    color: Colors.red,
                  ),
                ),
                Spacer(flex: 1),
                Expanded(
                  flex: 1,
                  child: Container(
                    color: Colors.green,
                  ),
                ),
              ],
            ),
          ),
        ),
      ],
    );
  }
}

class Spacer extends StatelessWidget {
  const Spacer({Key? key, this.flex = 1})
      : assert(flex != null),
        assert(flex > 0),
        super(key: key);

  final int flex;

  @override
  Widget build(BuildContext context) {
    return Expanded(
      flex: flex,
      child: const SizedBox.shrink(),
    );
  }
}

class CenterColumnRoute extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Column(
      crossAxisAlignment: CrossAxisAlignment.center,
      children: <Widget>[
        Text("hi"),
        Text("world"),
      ],
    );
  }
}
